1. Field of the Invention
This invention relates to the processing of sulfonic acids and is particularly concerned with converting such acids into a hydrocarbon oil of superior oxidation stability.
2. Description of the Prior Art
Petroleum fractions produced by physical separation and catalytic conversion of the components of crude oil contain appreciable quantities of undesirable impurities such as sulfur-containing compounds, olefins, oxygen-containing compounds, nitrogen-containing compounds and the like. These impurities affect the color, odor, stability and corrosive properties of the particular hydrocarbon oil in which they reside. One conventional method of removing some of these impurities is acid treating, the treatment of a petroleum fraction with sulfuric acid, oleum or sulfur trioxide. The action of these acid treating agents may be multiple. These agents may, for example, extract, sulfonate, sulfate, oxidize and polymerize, depending on the impurities present in the hydrocarbon oil undergoing treatment. Acid treatment will normally remove at least a portion of the sulfur and asphaltic or gum-like materials, improve color and stability, and to some extent improve the odor.
A frequent product of acid treatment is petroleum sulfonic acids produced by the sulfonation of hydrocarbons in the petroleum fraction treated by the sulfuric acid, oleum or sulfur trioxide. Aromatic hydrocarbons are easily sulfonated compared to saturated hydrocarbons of the paraffin and cycloparaffin series. Sulfonic acids are normally recovered from the acid treating process in the form of salts or petroleum sulfonates. Oil soluble petroleum sulfonates have wide industrial application as surface-active agents and are used as emulsifiers, dispersants, wetting agents and rust and corrosion inhibitors. These sulfonates are primary ingredients in such products as soluble cutting oils, textile oils, and rust preventatives.
A large quantity of petroleum sulfonates is produced as a by-product during the manufacture of technical and medicinal grade white oils. The feed to the white oil production process is normally some type of hydrocarbon base oil containing saturated aliphatic and naphthenic compounds unreactive to conventional acid treating agents, and aromatic compounds of all types; including one, two and three ring structures that may contain olefinic linkages and highly reactive appendages such as oxygen, nitrogen, sulfur and the like. The feed stock is treated with sulfuric acid, oleum or sulfur trioxide, which converts the highly reactive aromatics into sulfonic acids while having little effect on the unreactive saturated aliphatic and naphthenic compounds. After acid treatment, the acid sludge is separated from the oil phase and disposed of. The oil phase, which contains the oil soluble sulfonic acids, is neutralized and mixed with a solvent such as isopropanol or the like. The sulfonates produced when the oil-soluble sulfonic acids are neutralized dissolve in the solvent, which is then separated from the oil phase. The remaining hydrocarbons are known as white oils because of their purity, non-reactivity and absence of color. The separated solvent solution is normally mixed with an inert diluent oil and the mixture is heated to remove the solvent. The remaining product will normally contain between about 45 and 65 weight percent sulfonates and is normally sold in this form as natural petroleum sulfonates. These sulfonates are in actuality a diluted mixture of many diverse types of aromatic sulfonates.
In the past there have been periods of time when the demand for petroleum sulfonates was low and was far exceeded by the amount of sulfonic acids produced during acid treatment. If such a situation should arise again, it may be desirable to dispose of the sulfonic acids economically and in an ecologically acceptable manner without converting them to petroleum sulfonates, which may be difficult to sell because of low demand.